Spermidine, a positive modulator of the NMDA receptor, facilitates extinction and prevents the reinstatement of morphine-induced conditioned place preference in mice.

RATIONALE: Individuals with opioid use disorders often relapse into drug-seeking behavior after recalling memories linked to the drug use experience. Improving extinction efficacy has been used as a strategy to treat substance use disorders and suppress relapse. Although N-methyl-D-aspartate receptor (NMDAr) agonists facilitate acquisition, consolidation, and extinction, no study has addressed whether spermidine (SPD), a natural polyamine ligand of the NMDA receptor, facilitates the extinction and reinstatement of morphine-induced conditioned place preference (CPP). OBJECTIVES AND METHODS: The aim of the present study was to investigate the effect of SPD, an NMDAr agonist, on the extinction and reinstatement of morphine-induced CPP in mice. Adult male albino Swiss mice received saline (0.9% NaCl) or morphine (5 mg/kg) intraperitoneally (i.p.) and were respectively confined to a black or a white compartment for 30 min for four consecutive days for CPP induction. SPD (10-30 mg/kg, i.p.) or ifenprodil (NMDAr antagonist, 0.1-1 mg/kg, i.p.) were injected 15 min before extinction training. RESULTS: SPD and ifenprodil facilitated the extinction of morphine-induced CPP. SPD treatment during the extinction period impaired reinstatement induced by a priming dose of morphine (1.25 mg/kg). Ifenprodil (0.1 mg/kg) prevented the facilitatory effect of spermidine on the extinction of morphine-induced CPP but did not prevent reinstatement induced by morphine. CONCLUSIONS: These results suggest that SPD facilitated the extinction of morphine-induced CPP by modulating the polyamine binding site of the NMDA receptor. Our findings reveal important effects of SPD and ifenprodil on the re-exposure-induced decrease in morphine-induced CPP, which may be promising for developing novel pharmacological strategies to treat opioid use disorder.

Taurine Protects from Pentylenetetrazole-Induced Behavioral and Neurochemical Changes in Zebrafish.

Epilepsy is a common neurological disorder characterized by recurrent unprovoked seizures, which culminate in various neurobehavioral and neurochemical changes. Taurine (TAU) is an amino sulfonic acid which acts an endogenous inhibitory neuromodulator. Moreover, TAU displays intrinsic antioxidant activity, contributing to its beneficial actions in the CNS. Here, we evaluated whether TAU pretreatment protects from pentylenetetrazole (PTZ)-induced behavioral alterations and oxidative stress-related parameters in zebrafish brain tissue. Fish were pretreated with 42, 150, and 400 mg/L TAU (40 min) and further exposed to 10 mM PTZ (20 min) to analyze the seizure-like behaviors. As a positive control, another group was previously treated with 75 µM diazepam (DZP). Afterwards, biochemical experiments were performed. All TAU concentrations tested decreased seizure intensity in the first 150 s. Importantly, 150 mg/L TAU attenuated seizure-like behavioral scores, decreased seizure intensity, reduced the frequency of clonic-like seizures (score 4), and increased the latency to score 4. TAU (150 mg/L) also prevented oxidative stress in PTZ-challenged fish by decreasing lipid peroxidation and protein carbonylation and preventing changes on nonprotein thiol levels. No significant changes were observed in MTT assay and LDH activity. Differently than observed in DZP group, TAU did not affect the overall swimming activity of fish, suggesting different mechanisms of action. Collectively, we show that TAU attenuates PTZ-induced seizure-like behaviors and brain oxidative stress in zebrafish, suggesting the involvement of antioxidant mechanisms in neuroprotection.

Systemic delivery of selective EP1 and EP3 receptor antagonists attenuates pentylenetetrazole-induced seizures in mice.

Neuroinflammation plays a major role in brain excitability and may contribute to the development of epilepsy. Prostaglandin E2 (PGE2) is a direct mediator of inflammatory responses and, through EP receptors, plays an important role in neuronal excitability. Pharmacological evidence supports that centrally-administered EP1 and EP3 receptor antagonists reduced acutely evoked seizures in rats. Translation of these findings would benefit from evidence of efficacy with a more clinically relevant route of delivery and validation in another species. In the current study we investigated whether the systemic administration of EP1 and EP3 agonists and antagonists modulate pentylenetetrazole (PTZ)-induced seizures in mice. In addition, it was examined whether these compounds alter Na+, K+-ATPase activity, an enzyme responsible for the homeostatic ionic equilibrium and, consequently, for the resting membrane potential in neurons. While the systemic administration of EP1 and EP3 antagonists (ONO-8713 and ONO-AE3-240, respectively) attenuated, the respective agonists (ONO-DI-004 and ONO-AE-248) potentiated PTZ-induced seizures (all compounds injected at the dose of 10 µg/kg, s.c., 30 min before PTZ challenge). Co-administration of either EP1 or EP3 agonist with the respective antagonists nullified the anticonvulsant effects of EP1/3 receptor blockade. In addition, EP1 and EP3 agonists exacerbated PTZ-induced decrease of Na+, K+-ATPase activity in both cerebral cortex and hippocampus, whereas, EP1 and EP3 antagonists prevented PTZ-induced decrease of Na+, K+-ATPase activity in both structures. Our findings support and extend evidence that EP1 and EP3 receptors may be novel targets for the development of anticonvulsant drugs.

Spermine protects from LPS-induced memory deficit via BDNF and TrkB activation.

Lipopolysaccharide (LPS) has been long known to promote neuroinflammation and learning and memory deficits. Since spermine, one of the main natural polyamines in the central nervous system, protects from LPS-induced memory deficit by a mechanism that comprises GluN2B receptors, the aim of the present study was to determine whether brain-derived neurotrophic factor (BDNF), tropomyosin-related kinase B (TrkB) receptor and cAMP response element binding (CREB) are involved in this protective effect of spermine. Adult male Swiss albino mice received, immediately after training in the novel object recognition task, saline or LPS (250 µg/kg, i.p.); 5 min later they received saline or spermine (0.3 mg/kg, i.p.) and, when specified, 5 min thereafter saline or the TrkB receptor antagonist ANA-12 (0.5 mg/kg, i.p.) in different flanks. Animals were tested 24 h after training. Spermine protected from LPS-induced memory deficit and this protective effect was reversed by ANA-12. In a subset of animals BDNF, CREB and phospho-CREB immunoreactivity was determined in the hippocampi and cerebral cortex 4 h after spermine injection. Spermine reversed the decrease of mature BDNF levels induced by LPS in both hippocampus and cerebral cortex. Spermine increased phospho-CREB content and phospho-CREB/total CREB ratio in the cerebral cortex of LPS-treated mice. The results support that the protective effect of spermine on LPS-induced memory deficits depends on TrkB receptor activation and is accompanied by restoration of mature BDNF levels in hippocampus and cerebral cortex, as well as increased CREB phosphorylation in the cerebral cortex.

Spermidine improves the persistence of reconsolidated fear memory and neural differentiation in vitro: Involvement of BDNF.

Putrescine, spermidine and spermine are organic cations implicated in learning, memory consolidation, reconsolidation and neurogenesis. These physiological processes are closely related, and convincing evidence indicates that neurogenesis is implicated both, in the establishment and maintenance of remote contextual fear memory. Although brain-derived neurotrophic factor (BDNF) is a key mediator involved in both neurogenesis and memory consolidation, effects of spermidine on persistence of memory after reactivation (reconsolidation) and possible involvement of BDNF have not been investigated. Here, we investigated whether the intrahippocampal infusion of spermidine improves the persistence of reconsolidated contextual fear conditioning memory in rats and whether these possible changes depend on BDNF/TrkB signaling in the hippocampus. The infusion of spermidine immediately and 12h post-reactivation improved fear memory of the animals tested seven but not two days after reactivation. The facilitatory effect of spermidine on the persistence of reconsolidated memory was blocked by the TrkB inhibitor ANA-12 (73.6pmol/site) and accompanied by mature BDNF level increase in the hippocampus, indicating that it depends on the BDNF/TrkB pathway. We also investigated whether spermidine alters BDNF levels and neural progenitor cell differentiation in vitro. Spermidine increased BDNF levels in vitro, facilitating neuritogenesis and neural migration. Spermidine-induced neuritogenesis in vitro was also blocked by ANA-12 (10µM). Since spermidine increases BDNF levels and facilitates neural differentiation in vitro, similar mechanisms may be involved in spermidine-induced facilitation of the persistence of reconsolidated memory.

Intrahippocampal infusion of spermidine improves memory persistence: Involvement of protein kinase A.

Spermidine (SPD) is an endogenous aliphatic amine that modulates GluN2B-containing NMDA receptors and improves memory. Recent evidence suggests that systemic SPD improves the persistence of the long term memory of fear. However, the role of hippocampal polyamines and its binding sites in the persistence of fear memory is to be determined, as well as its putative underlying mechanisms. This study investigated whether the intrahippocampal (i.h.) infusion of spermidine or arcaine, modulators of polyamine binding site at GluN2B-containing NMDA receptors, alters the persistence of the memory of contextual fear conditioning task in rats. We also investigated whether protein synthesis and cAMP dependent protein kinase (PKA) play a role in SPD-induced improvement of the fear memory persistence. While 12h post-training infusion of spermidine facilitated, arcaine and the inhibitor of protein synthesis (anisomycin) impaired the memory of fear assessed 7days after training. The infusion of arcaine, anisomycin or a selective PKA inhibitor (H-89), at doses that have no effect on memory per se, prevented the SPD-induced improvement of memory persistence. H-89 prevented the stimulatory effect of SPD on phospho-PKA/total-PKA ratio. These results suggests that the improvement of fear memory persistence induced by spermidine involves GluN2B-containing NMDA receptors, PKA pathway and protein synthesis in rats.

Monoterpenoid terpinen-4-ol exhibits anticonvulsant activity in behavioural and electrophysiological studies.

Terpinen-4-ol (4TRP) is a monoterpenoid alcoholic component of essential oils obtained from several aromatic plants. We investigated the psychopharmacological and electrophysiological activities of 4TRP in male Swiss mice and Wistar rats. 4TRP was administered intraperitoneally (i.p.) at doses of 25 to 200 mg/kg and intracerebroventricularly (i.c.v.) at concentrations of 10, 20, and 40 ng/2 µL. For in vitro experiments, 4TRP concentrations were 0.1 mM and 1.0 mM. 4TRP (i.p.) inhibited pentylenetetrazol- (PTZ-) induced seizures, indicating anticonvulsant effects. Electroencephalographic recordings showed that 4TRP (i.c.v.) protected against PTZ-induced seizures, corroborating the behavioural results. To determine whether 4TRP exerts anticonvulsant effects via regulation of GABAergic neurotransmission, we measured convulsions induced by 3-mercapto-propionic acid (3-MP). The obtained results showed involvement of the GABAergic system in the anticonvulsant action exerted by 4TRP, but flumazenil, a selective antagonist of the benzodiazepine site of the GABAA receptor, did not reverse the anticonvulsant effect, demonstrating that 4TRP does not bind to the benzodiazepine-binding site. Furthermore, 4TRP decreased the sodium current through voltage-dependent sodium channels, and thus its anticonvulsant effect may be related to changes in neuronal excitability because of modulation of these channels.

Spermidine improves fear memory persistence.

Persistence is the most characteristic attribute of long-term memory (LTM). For memory persistence, a second late event of consolidation, that occurs around 12h after the acquisition, is necessary. Although the N-methyl-d-aspartate (NMDA) receptor has been involved in the persistence of memory, whether endogenous modulators of the NMDA receptor actually modulate memory persistence is unknown. In the current study we investigated whether spermidine and arcaine, respectively agonist and antagonist of polyamine binding site at NMDA receptor, alter the persistence of the memory of contextual fear conditioning task in rats. While 12h post-training administration of spermidine (10 and 30mg/kg, i.p.) facilitated, arcaine (10mg/kg, i.p.) impaired the memory of fear assessed 2 and 7 days after training. Arcaine (0.1mg/kg) prevented the facilitatory effect of spermidine (10mg/kg, i.p.), and spermidine (1mg/kg), prevented the memory impairment induced by arcaine (10mg/kg, i.p.) when tested 2 and 7 days after training. These results suggest that endogenous polyamines improve the persistence of fear memory.

Selegiline reverses aß25₋35-induced cognitive deficit in male mice.

Alzheimer's disease (AD) is biochemically characterized by the occurrence of extracellular deposits of amyloid beta peptide (Aß) and intracellular deposits of the hyperphosphorylated tau protein, which are causally related to the pathological hallmarks senile plaques and neurofibrillary tangles. Monoamine oxidase B (MAO-B) activity, involved in the oxidation of biogenic monoamines, is particularly high around the senile plaques and increased in AD patients in middle to late clinical stages of the disease. Selegiline is a selective and irreversible MAO-B inhibitor and, although clinical trials already shown the beneficial effect of selegiline on cognition of AD patients, its mechanism of action remains to be elucidated. Therefore, we first investigated whether selegiline reverses the impairment of object recognition memory induced by Aß25-35 in mice, an established model of AD. In addition, we investigated whether selegiline alters MAO-B and MAO-A activities in the hippocampus, perirhinal and remaining cerebral cortices of Aß25-35-injected male mice. Acute (1 and 10 mg/kg, p.o., immediately post-training) and subchronic (10 mg/kg, p.o., seven days after Aß25-35 injection and immediately post-training) administration of selegiline reversed the cognitive impairment induced by Aß25-35 (3 nmol, i.c.v.). Acute administration of selegiline (1 mg/kg, p.o.) in combination with Aß25-35 (3 nmol) decreased MAO-B activity in the perirhinal and remaining cerebral cortices. Acute administration of selegiline (10 mg/kg, p.o.) decreased MAO-B activity in hippocampus, perirhinal and remaining cerebral cortices, regardless of Aß25-35 or Aß35-25 treatment. MAO-A activity was not altered by selegiline or Aß25-35. In summary, the current findings further support a role for cortical monoaminergic transmission in the cognitive deficits observed in AD.

Accumulation, elimination, and effects of parenteral exposure to aluminum in newborn and adult rats.

Aluminum (Al) delivered to preterm infants via parenteral nutrition may exceed the limit of 5 µg/kg/day set by the US Food and Drug Administration. This study evaluated the effect of the administration of an equivalent amount of Al (0.12 mg/kg/day) to newborn rats. The study included the administration of a higher amount of Al (24.8 mg/kg/day) not only to newborn rats but also to adult (2- and 4-month-old) rats. Aluminum was intraperitoneally administered for a period of 10 days. Newborn animals were evaluated for developmental changes every day starting from the second day after birth. Twenty days after the last administration, 10 animals were killed and their organs were removed; the remainders were killed on day 40. A dosage of 24.8 mg/kg/day was administered to the two groups of adult rats, which were killed following the same protocol after 20 and 40 days. The results of physical parameters and developmental and behavioral tests were not conclusive and no significant differences were observed between the lower and higher Al dose and control groups. The group that received 0.12 mg/kg/day showed significant differences in Al accumulation only in the liver and muscle. The groups that received a higher dose of Al showed an accumulation in all tissues among all age groups studied, but the newborn group showed the greatest accumulation (results for day 20). After 40 days, Al content in all tissues decreased more than 50% in this group, whereas among the adults, the Al content increased or remained constant. An increase in age correlated with a lower elimination rate. Considering the ongoing human Al exposure, along with its age-related elimination rate, Al accumulation in the body may be long-lasting.

Piracetam prevents scopolamine-induced memory impairment and decrease of NTPDase, 5'-nucleotidase and adenosine deaminase activities.

Piracetam improves cognitive function in animals and in human beings, but its mechanism of action is still not completely known. In the present study, we investigated whether enzymes involved in extracellular adenine nucleotide metabolism, adenosine triphosphate diphosphohydrolase (NTPDase), 5'-nucleotidase and adenosine deaminase (ADA) are affected by piracetam in the hippocampus and cerebral cortex of animals subjected to scopolamine-induced memory impairment. Piracetam (0.02 µmol/5 µL, intracerebroventricular, 60 min pre-training) prevented memory impairment induced by scopolamine (1 mg/kg, intraperitoneal, immediately post-training) in the inhibitory avoidance learning and in the object recognition task. Scopolamine reduced the activity of NTPDase in hippocampus (53 % for ATP and 53 % for ADP hydrolysis) and cerebral cortex (28 % for ATP hydrolysis). Scopolamine also decreased the activity of 5'-nucleotidase (43 %) and ADA (91 %) in hippocampus. The same effect was observed in the cerebral cortex for 5'-nucleotidase (38 %) and ADA (68 %) activities. Piracetam fully prevented scopolamine-induced memory impairment and decrease of NTPDase, 5'-nucleotidase and adenosine deaminase activities in synaptosomes from cerebral cortex and hippocampus. In vitro experiments show that piracetam and scopolamine did not alter enzymatic activity in cerebral cortex synaptosomes. Moreover, piracetam prevented scopolamine-induced increase of TBARS levels in hippocampus and cerebral cortex. These results suggest that piracetam-induced improvement of memory is associated with protection against oxidative stress and maintenance of NTPDase, 5'-nucleotidase and ADA activities, and suggest the purinergic system as a putative target of piracetam.

Spermidine-induced improvement of memory involves a cross-talk between protein kinases C and A.

Spermidine (SPD) is an endogenous aliphatic amine with polycationic structure that modulates NMDA receptor activity and improves memory. Recent evidence suggests that cAMP-dependent protein kinase (PKA) and cAMP response element-binding protein (CREB) play a role in SPD-induced improvement of memory. In the current study, we determined whether the calcium-dependent protein kinase (PKC) signaling pathway is involved in SPD-induced facilitation of memory of inhibitory avoidance task in adult rats. The post-training administration of the PKC inhibitor, 3-[1-(dimethylaminopropyl)indol-3-yl]-4-(indol-3-yl)maleimide hydrochloride [GF 109203X, 2.5 ρmol, intrahippocampal (ih)] with SPD (0.2 nmol, ih) prevented memory improvement induced by SPD. Intrahippocampal administration of SPD (0.2 nmol) facilitated PKC phosphorylation in the hippocampus, 30 min after administration. GF 109203X prevented not only the stimulatory effect of SPD on PKC but also PKA and CREB phosphorylation. These results suggest that memory enhancement induced by the ih administration of SPD involves the cross-talk between PKC and PKA/CREB, with sequential activation of PKC and PKA/CREB pathways, in rats.

Spermidine decreases Na⁺,K⁺-ATPase activity through NMDA receptor and protein kinase G activation in the hippocampus of rats.

Spermidine is an endogenous polyamine with a polycationic structure present in the central nervous system of mammals. Spermidine regulates biological processes, such as Ca(2+) influx by glutamatergic N-methyl-d-aspartate receptor (NMDA receptor), which has been associated with nitric oxide synthase (NOS) and cGMP/PKG pathway activation and a decrease of Na(+),K(+)-ATPase activity in rats' cerebral cortex synaptosomes. Na(+),K(+)-ATPase establishes Na(+) and K(+) gradients across membranes of excitable cells and by this means maintains membrane potential and controls intracellular pH and volume. However, it has not been defined whether spermidine modulates Na(+),K(+)-ATPase activity in the hippocampus. In this study we investigated whether spermidine alters Na(+),K(+)-ATPase activity in slices of hippocampus from rats, and possible underlying mechanisms. Hippocampal slices and homogenates were incubated with spermidine (0.05-10 µM) for 30 min. Spermidine (0.5 and 1 µM) decreased Na(+),K(+)-ATPase activity in slices, but not in homogenates. MK-801 (100 and 10 µM), a non-competitive antagonist of NMDA receptor, arcaine (0.5µM), an antagonist of the polyamine binding site at the NMDA receptor, and L-NAME (100µM), a NOS inhibitor, prevented the inhibitory effect of spermidine (0.5 µM). ODQ (10 µM), a guanylate cyclase inhibitor, and KT5823 (2 µM), a protein kinase G inhibitor, also prevented the inhibitory effect of spermidine on Na(+),K(+)-ATPase activity. Spermidine (0.5 and 1.0 µM) increased NO(2) plus NO(3) (NOx) levels in slices, and MK-801 (100 µM) and arcaine (0.5 µM) prevented the effect of spermidine (0.5 µM) on the NOx content. These results suggest that spermidine-induced decrease of Na(+),K(+)-ATPase activity involves NMDA receptor/NOS/cGMP/PKG pathway.

Trypanosoma evansi: concentration of 3-nitrotyrosine in the brain of infected rats.

Nitric oxide (NO) is involved in many physiological processes, such as blood pressure control, neurotransmission, inhibition of platelet and neutrophil adherence, and the ability to kill tumor cells and parasites. The indirect determination of NO can be made by detection of 3-nitrotyrosine (3-NT) residues. The aim of this study was to measure the concentration of 3-NT in the brain of rats experimentally infected with Trypanosoma evansi. Twenty-four were inoculated intraperitoneally with cryopreserved blood containing 1×10(6) trypomastigotes per animal. Twenty-four animals were used as negative controls and received 0.2 mL of saline by the same route. The experimental groups (group C and T) were established according to the time after infection and the degree of parasitemia as follows: four control subgroups (C3, C5, C10 and C20) with six non-inoculated animals each and four test subgroups (T3, T5, T10 and T20) with six animals infected with T. evansi in each group. The animals were anesthetized with isoflurane and subsequently euthanized at the days 3 (C3, T3), 5 (C5, T5), 10 (C10, T10) and 20 (C20, T20) post-infection (PI). The brain was removed and dissected into cerebellum, cerebral cortex, striatum and hippocampus. Concentration of 3-NT in the brain was determined by Slot blot technique. At the day 3 PI no changes were observed in the concentration of 3-NT among the groups. There was a significant reduction (p<0.05) of 3-NT concentration in the striatum and cerebellum at the days 5 and 10 PI, respectively. At the day 20 PI a significant increase (p<0.05) of 3-NT was observed in the cerebellum, cerebral cortex and hippocampus from the infected animals. Therefore, T. evansi infection caused changes in the concentrations of 3-NT in the central nervous system (CNS), which may be related to clinical signs and infection management.

Chronic deficit in the expression of voltage-gated potassium channel Kv3.4 subunit in the hippocampus of pilocarpine-treated epileptic rats.

Voltage gated K(+) channels (Kv) are a highly diverse group of channels critical in determining neuronal excitability. Deficits of Kv channel subunit expression and function have been implicated in the pathogenesis of epilepsy. In this study, we investigate whether the expression of the specific subunit Kv3.4 is affected during epileptogenesis following pilocarpine-induced status epilepticus. For this purpose, we used immunohistochemistry, Western blotting assays and comparative analysis of gene expression using TaqMan-based probes and delta-delta cycle threshold (ΔΔCT) method of quantitative real-time polymerase chain reaction (qPCR) technique in samples obtained from age-matched control and epileptic rats. A marked down-regulation of Kv3.4 immunoreactivity was detected in the stratum lucidum and hilus of dentate gyrus in areas corresponding to the mossy fiber system of chronically epileptic rats. Correspondingly, a 20% reduction of Kv3.4 protein levels was detected in the hippocampus of chronic epileptic rats. Real-time quantitative PCR analysis of gene expression revealed that a significant 33% reduction of transcripts for Kv3.4 (gene Kcnc4) occurred after 1 month of pilocarpine-induced status epilepticus and persisted during the chronic phase of the model. These data indicate a reduced expression of Kv3.4 channels at protein and transcript levels in the epileptic hippocampus. Down-regulation of Kv3.4 in mossy fibers may contribute to enhanced presynaptic excitability leading to recurrent seizures in the pilocarpine model of temporal lobe epilepsy.

Standardized extract of Dicksonia sellowiana Presl. Hook (Dicksoniaceae) decreases oxidative damage in cultured endothelial cells and in rats.

AIMS: Aging and a variety of pathologies, including cancer, diabetes, cardiovascular and inflammatory diseases have been associated with reactive oxygen species (ROS), such as superoxide anion (O2·â»), hydroxyl radical (·OH) and hydrogen peroxide (H2O2) generation. Plant polyphenols bear radical scavenging/antioxidant activity. A phytomedicinal preparation obtained from aerial parts of Dicksonia sellowiana (Dicksoniaceae), a native plant from Central and South America, has been widely used in Brazil against asthma and presents beneficial effects in several other diseases, including cardiovascular disturbance. In this work, we investigated whether Dicksonia sellowiana, which is also known to contain high levels of polyphenols, presents antioxidant activity. METHODS: The antioxidant activity of the hydroalcoholic extract obtained from Dicksonia sellowiana leaves (HEDS) was investigated by in vitro and in vivo tests. RESULTS: HEDS (0.1-100 µg/mL) exhibited a strong scavenging activity against all reactive species tested (DPPH, O2·â»,·OH and H2O2; IC50=6.83±2.05, 11.6±5.4, 2.03±0.4, and 4.8±0.4 µg/mL, respectively). HEDS strongly protected endothelial cells against H2O2-induced oxidative stress by mechanisms other than increasing catalase activity. In addition, HEDS protected cell membrane from oxidative damage. HEDS, (20 and 40 mg/kg) inhibited lipid peroxidation in vivo (29.8% and 24.5%, respectively). CONCLUSIONS: According to our results, we can speculate that the traditional uses of Dicksonia sellowiana for cardiovascular diseases, asthma and skin diseases could be, at least in part, related to the potent antioxidant and endothelial protective activities of the plant.

Altered expression and function of small-conductance (SK) Ca(2+)-activated K+ channels in pilocarpine-treated epileptic rats.

Small conductance calcium (Ca(2+)) activated SK channels are critical regulators of neuronal excitability in hippocampus. Accordingly, these channels are thought to play a key role in controlling neuronal activity in acute models of epilepsy. In this study, we investigate the expression and function of SK channels in the pilocarpine model of mesial temporal lobe epilepsy. For this purpose, protein expression was assessed using western blotting assays and gene expression was analyzed using TaqMan-based probes and the quantitative real-time polymerase chain reaction (qPCR) comparative method delta-delta cycle threshold ( big up tri, open big up tri, openCT) in samples extracted from control and epileptic rats. In addition, the effect of SK channel antagonist UCL1684 and agonist NS309 on CA1 evoked population spikes was studied in hippocampal slices. Western blotting analysis showed a significant reduction in the expression of SK1 and SK2 channels at 10days following status epilepticus (SE), but levels recovered at 1month and at more than 2months after SE. In contrast, a significant down-regulation of SK3 channels was detected after 10days of SE. Analysis of gene expression by qPCR revealed a significant reduction of transcripts for SK2 (Kcnn1) and SK3 (Kcnn3) channels as early as 10days following pilocarpine-induced SE and during the chronic phase of the pilocarpine model. Moreover, bath application of UCL1684 (100nM for 15min) induced a significant increase of the population spike amplitude and number of spikes in the hippocampal CA1 area of slices obtained control and chronic epileptic rats. This effect was obliterated by co-administration of UCL1684 with SK channel agonist NS309 (1microM). Application of NS309 failed to modify population spikes in the CA1 area of slices taken from control and epileptic rats. These data indicate an abnormal expression of SK channels and a possible dysfunction of these channels in experimental MTLE.

Spermine improves recognition memory deficit in a rodent model of Huntington's disease.

Huntington's disease (HD) is a progressive neurodegenerative disorder associated with motor and cognitive impairment. Intrastriatal administration of quinolinic acid (QA) causes neurodegeneration, glial proliferation and cognitive impairment in animals, which are similar to these seen in human HD. Since polyamines improve memory in cognitive tasks, we now tested if the post-training intrastriatal administration of spermine, an agonist of the polyamine site at the NMDA receptor, reverses the deficits in the object recognition task induced by QA. Bilateral striatal injections of QA (180 or 360 nmol/site) caused object recognition impairment, neuronal death and reactive astrogliosis. A single injection of spermine (0.1 and 1 nmol/site), 5 days after QA injection, reversed QA-induced impairment of object recognition task. Spermine (0.1 nmol/site) also inhibited QA-induced reactive astrogliosis measured by a semi-quantitative determination of GFAP immunolabelling, but did not alter neuronal death, measured by a semi-quantitative determination of fluoro-Jade C staining. These results suggest that polyamine binding sites may be considered a novel therapeutic target to prevent reactive astrogliosis and mnemonic deficits in HD.

Effect of 5-trifluoromethyl-4,5-dihydro-1H-pyrazoles on chronic inflammatory pain model in rats.

Nonsteroidal antiinflammatory drugs (NSAIDs) are commonly used for treatment of arthritis. However, their long-term use has been associated with considerable morbidity, limiting their application. Thus, there remains a need to develop new drugs for the effective and safe relief of chronic inflammatory pain. In this context, the present study was designed to evaluate the antinociceptive and antiedematogenic effects of the 5-trifluoromethyl-4,5-dihydro-1H-pyrazole derivatives EPFCA3 and MPFCA4 after acute (1-1000 micromol/kg) and chronic (100 micromol/kg for 15 days) administration in rats submitted to a model of adjuvant-induced arthritis. We also analyzed some biochemical indicators of toxicity (alanine aminotransferase, aspartate aminotransferase, urea and creatinine levels) after prolonged administration of these compounds. We found that acute and chronic subcutaneuous administration of EPFCA3 and MPFCA4 produces an antinociceptive, but not antiedematogenic, effect on the arthritis animal model induced by complete Freund's adjuvant (CFA). No signs of toxicity were observed in the animals chronically treated with EPFCA3 or MPFCA4. Dipyrone (1-1000 micromol/kg) was used as the positive control and its effect was similar to that of the novel pyrazoles. The activity of tissue myeloperoxidase, the tissue TNF-alpha level and the serum haptoglobin level was increased by intraplantar CFA injection. However, chronic administration of EPFCA3, MPFCA4 or dipyrone was not able to alter the relation between these parameters and inflammation. Our results suggest that EPFCA3 and MPFCA4 are good candidates for the development of new drugs for pain treatment.

Antinociceptive action of 4-methyl-5-trifluoromethyl-5-hydroxy-4, 5-dihydro-1H-pyrazole methyl ester in models of inflammatory pain in mice.

AIMS: The aim of the present study was to evaluate the antinociceptive effect of the novel pyrazoline methyl ester: 4-methyl-5-trifluoromethyl-5-hydroxy-4,5-dihydro-1H-pyrazole methyl ester (MPF4). MAIN METHODS: The effect of MPF4 was assessed in two models of pain: arthritic pain caused by Complete Freund's Adjuvant (CFA) and postoperative pain caused by surgical incision in mice. KEY FINDINGS: MPF4 given intraperitoneally (1.0 mmol/kg, i.p.) produced marked antinociception in inflammatory allodynia caused by CFA. The antinociceptive effect produced by MPF4 was reversed with the pre-treatment of animals with naloxone or naltrindole. Oral administration of MPF4 (1.0 mmol/kg, p.o), dipyrone (1.0 mmol/kg, p.o.) and morphine (0.026 mmol/kg, p.o.) also produced an anti-allodynic effect. However, none of the compounds evaluated reversed the paw edema produced by CFA. Moreover, MPF4, dipyrone and morphine also produced an anti-allodynic effect in the surgical incisional pain model. The maximal inhibitions obtained with preemptive drug treatment were 66+/-7%, 73+/-9% and 88+/-8% for MPF4 (1.0 mmol/kg, p.o.), dipyrone (1.0 mmol/kg, p.o.) and morphine (0.026 mmol/kg, p.o.), respectively. The maximal inhibitions obtained with curative drug treatment were 53+/-9%, 83+/-7% and 84+/-7%, for MPF4, dipyrone and morphine, respectively. Unlike indomethacin, MPF4 did not induce gastric lesions at the dose that caused the highest antinociception (1.0 mmol/kg, p.o). The anti-allodynic action of MPF4, dipyrone and morphine was not associated with impairment of motor activity. SIGNIFICANCE: The results of the present study suggest that MPF4 represents a potential target for the development of new drugs to treat persistent inflammatory pain.